1. Technical Field
The present invention relates to cable television decoders, and in particular to a method and system for detecting unauthorized utilization of cable television decoders. Still more particularly, the present invention relates to detecting unauthorized utilization of a cable television decoder by determining a local oscillator frequency of the decoder, and determining whether the decoder is authorized to receive a particular cable television channel associated with the determined local oscillator frequency.
2. Description of the Related Art
Cable television decoders are utilized to receive both cable and regular broadcast television signals. Cable television signals are typically encoded utilizing a predetermined scrambling technique. A decoder is coupled to a user's television and is designed to receive and decode the scrambled signal. Once the signal is decoded, it is transmitted to the television where it is presented to the user.
A television is capable of receiving a regular broadcast signal utilizing a receiver which includes a local oscillator. The local oscillator is tuned by a user to one of a variety of channel frequencies associated with the television channel the user desires to watch. When the user has paid for cable service, the television is typically permanently set to one channel, often channel 2 or 3. The television is then coupled to a decoder supplied by the cable provider. The decoder, instead of the television, is then tuned, utilizing the decoder's local oscillator, to a channel frequency associated with the cable television channel the user desires to watch. The signal input to the decoder is provided by the cable television provider via a cable coupled to the decoder.
Many different types of decoders are available. Each type of decoder utilizes a different local oscillator frequency for each channel. For example, channel 2 may be associated with a local oscillator frequency of 650.125 MHz for one decoder and with a local oscillator frequency of 650.250 MHz for a second decoder.